Antiretroviral therapy (ART) increases life expectancy and quality of life for individuals infected with HIV, and can reduce the chance of HIV transmission, but a high degree of adherence to ART is required to achieve these benefits for most people. Unfortunately, only 59% of patients in North America report ART adherence >90%. Thus, ART adherence interventions are a critical part of the fight against HIV/AIDS. Injection drug use and crack cocaine use are major factors in the transmission of HIV, and are associated with non-adherence to ART. Several types of interventions, most notably directly administered antiretroviral therapy (direct observation of antiretroviral administration and patien supports) and contingency management (the provision of incentives contingent upon objective evidence of adherence) have been effective in promoting short-term ART adherence in drug users. However, a core problem with all ART adherence interventions is that their effects do not last after the interventions are discontinued. The common finding of post-intervention dissipation of effects suggests that ART adherence interventions may need to be implemented as long-term or even permanent adjuncts to ART for drug users. A Stage 1 Behavior Therapy Development project is planned over 2 years to develop an intensive intervention that incorporates the most effective techniques for promoting ART adherence in drug users, and delivers them in a manner that allows for their large-scale implementation as long-term or even permanent adjuncts to ART. This ART adherence intervention will bundle a targeted group of effective component interventions into a Smartphone application that is easy for patients to use, simple to manage, and maximally convenient for all stakeholders. Our ultimate goal is to produce an intervention that is highly effective and scalable. Toward that end, the intervention to be developed under this project will be largely automated and will (1) facilitate consultation with care providers (2) provide reminders when a dose is overdue, (3) provide electronic remote observation of medication-taking, and (4) reward ART adherence (Consult-Remind-Observe-reWard; CROW). The proposed intervention is highly innovative: no previous ART adherence intervention has involved direct observation of medication administration and contingency management, despite their respective effectiveness in isolation. Importantly, no mobile/remote intervention currently under development is as intensive as CROW. In addition to developing this Smartphone-based intervention, a pilot study will be conducted in 50 HIV+ adults with a detectable viral load who are enrolled in opiate agonist pharmacotherapy. In this pilot study, participants will be randomly assigned to receive usual care, or usual care plus the CROW Smartphone intervention. The data from this pilot study will serve to demonstrate the feasibility and acceptability of the intervention, and to provide efficacy data necessary to plan a full-scaled randomized controlled trial. Overall, the CROW intervention could fill the urgent need for a highly effective and scalabl long-term intervention to increase adherence to antiretroviral therapy in drug users.